The U.S. Department of Health &Human Services and the National Recreation &Park Association both recommend Yoga as a form of total-solution exercise for older adults, capable of providing cardiovascular fitness, resistance training for muscle strength &bone health, and flexibility for functional range of motion as well as relaxation... Despite these dramatic claims of improved function across a variety of physiological &psychological systems/little is understood regarding the physical demands, program efficacy, and overall safety of Yoga for older adults. Our clinical trial experiences suggest that without proper evidenced-based prescription, Yoga participation can be ineffective or even injurious for elders. Thus, this application proposes an intervention development study (IDS) that will use biomechanical investigation (high-speed cameras, force platforms and musculoskeletal modeling) to quantify the physical demands of Yoga performance by older adults. In addition, the IDS will use physical-performance testing, muscle-performance testing, flexibility &balance assessments, and self-reports/to quantify the efficacy and safety of a 32-week Yoga program for ambulatory seniors. The Yoga program is divided into introductory and advanced phases/each lasting 16 weeks. The participants (N=24;65-90 years of age) will learn the associated Yoga poses (asanas) from Yoga instructors with expertise working with seniors. In order to quantify the dosage (physical demands) of the program, the participants will perform the asanas at the beginning and termination of each phase/while instrumented for biomechanical analysis. Follow-up physical performance, balance, and quality of life, assessments will be conducted at the end of each phase in order to determine the efficacy of the program. Outcome measures will include biomechanical indices of the physical demands associated with Yoga (joint range-of-motion, reaction forces, &moments), measures of muscular &functional performance (stair climb, chair stand, gait, strength, static &dynamic balance), adherence, and safety. Data from the IDS will be used to develop evidenced-based Yoga prescriptions, which we postulate will be associated with fewer musculoskeletal side effects compared to non-evidence based Yoga programs. We also postulate that evidenced-based tailoring of Yoga for seniors will enhance adherence and efficacy. The programs developed from this IDS will be tested in an expanded, Phase II, Randomized Controlled Trial. PUBLIC HEALTH RELEVANCE. Yoga is currently being recommended to restore and preserve strength, flexibility, balance, &physical capacity in older adults;however, our clinical trial experiences suggest that without proper evidenced-based prescription, Yoga participation can be ineffective or even injurious for seniors. To address this lack of evidence-based knowledge, the proposed IDS will: 1) quantify the physical demands of a 32-wk Yoga program designed for independent ambulatory seniors;2) characterize the relations between these demands and participant physical characteristics;3) examine the adherence, efficacy, &safety of the program;and 4) characterize the relations among reported adverse events, baseline participant characteristics, and Yoga physical demands.